Soil pH in St. Louis, MN: Lime or Sulfur?
Typical topsoil pH in St. Louis, MN
Typical topsoil in St. Louis, MN is pH 5.5, too acidic for vegetable garden. Expect roughly 11.5 lb of lime per 100 sq ft, but only after a soil test confirms it.
What St. Louis needs, by plant
- Already in range: potatoes, strawberries, blueberries, azaleas and rhododendrons, blue hydrangeas.
- Lime: lawn (cool-season grass) 11.5 lb/100 sq ft over 3 applications; vegetable garden 11.5 lb/100 sq ft over 3 applications; tomatoes 11.5 lb/100 sq ft over 3 applications; roses 11.5 lb/100 sq ft over 3 applications; pink hydrangeas 9.2 lb/100 sq ft over 2 applications.
What to do next
If your test confirms pH near 5.5, spread about 115 lb of ground limestone per 1,000 sq ft of vegetable bed in 3 doses, ideally in fall.
How mixed the soil is
Of the 3,057,239 surveyed acres in St. Louis, MN, 49% are moderately acidic (5.5-6.5), 43% are strongly acidic (below 5.5), 5% are near neutral (6.5-7.3), 3% are alkaline (above 7.3). Mapped soils run from pH 4.2 to 8, a spread of 3.8 units across 3,197 soil components. No single class covers 60% of the county, so two gardens a few miles apart here can need opposite treatments. Test your own bed.
Clay, organic matter and rates
Topsoil here averages 14.2% clay and 5.86% organic matter, which this site treats as clay. At 5.86% organic matter the soil buffers like a heavier one, which pushes it into the clay bracket. Moving it one pH unit takes about 11.5 lb of lime or 3.4 lb of sulfur per 100 sq ft. 3% of mapped components carry free carbonate (lime already in the ground).
St. Louis against the rest of Minnesota
pH 5.5 is 1.14 below the Minnesota median of 6.64. 3 of 87 Minnesota counties have more acidic topsoil. Nationally it is more acidic than the US county median of 6.05.
Closest in pH within the state: Cook (5.21), Crow Wing (5.35), Lake (5.36), Carlton (5.59), Pine (5.84), Chisago (5.87), Kanabec (5.91).
The range in Minnesota runs from Cook at 5.21 to Swift at 7.49; St. Louis sits 13% of the way up.